The present invention relates to a method and an apparatus for controlling a continuously variable transmission of an automotive vehicle.
In a method for controlling a continuously variable V-belt transmission which was previously proposed in pending Japanese Patent Application No. 56-44749 filed Mar. 28, 1981 which corresponds to U.S. patent application Ser. No. 362,489 filed Mar. 26, 1982 and commonly assigned herewith, a shift pattern was prememorized for throttle opening degree and vehicle speed, a proper reduction ratio command signal was retrieved versus actual throttle opening degree and vehicle speed, and the shift motor was controlled in accordance with this reduction ratio command signal to accomplish a desired reduction ratio. The shift motor which actuates a shift control valve to determine oil pressures to be supplied to the drive and driven pulley cylinder chambers, was controlled to rotate at a predetermined constant speed. As a result, with this controlling method, even if the accelerator pedal was depressed rapidly for the purpose of effecting a rapid acceleration, the shift motor did not increase its revolution speed and rotated at the predetermined constant speed, causing a sluggish shifting to a new reduction ratio, resulting in an acceleration short of a desired acceleration, thus failing to meet the demand by driver, and thus this is not preferrable from the standpoint of safety. To cope with this problem, it is conceivable to rotate the shift motor always at a high revolution speed, but, with this measure, the shift operating mechanism and the V-belt are always subject to a rapid change in stress, thus decreasing their life, and another problem is that ride feel during normal driving state gets worse because the response to shifting becomes excessively quick so that the actual shifting takes place even when the accelerator pedal is slightly depressed.